Stabilized aqueous suspension of phthalimidomethyl mono thio-or dithio- phosphates or phosphonates

ABSTRACT

WHEREIN X is oxygen or sulfur, R is alkyl having 1 to 4 carbon atoms and R1 is alkyl having 1 to 4 carbon atoms or alkoxy having 1 to 4 carbons (2) water and (3) phosphoric acid.   A stable insecticidal mixture comprising (1) phthalimidomethyl mono thio- or dithio-phosphates or phosphonates having the structural formula

United States Patent [191 Freiberg et al.

[ Nov. 5, 1974 STABILIZED AQUEOUS SUSPENSION OF PIITI-IALIMIDOMETHYLMONO THIO-OR DITHIO- PHOSPHATES OR PHOSPHONATES [75] Inventors: AshleyHerman Freiberg, Santa Clara, Calif.; David James Broadbent, Racine,Wis.

[73] Assignee: Stauffer Chemical Company, New

York, NY.

22 Filed: July 18, 1972 [211 Appl. No.: 272,818

Primary Examiner-Albert T. Meyers Assistant Examiner-D. W. RobinsonAttorney, Agent, or Firm-Edwin H. Baker [57] ABSTRACT A stableinsecticidal mixture comprising (1) phthalimidomethyl mono thioordithio-phosphates or phosphonates having the structural formula OR C\Non s i C -II wherein X is oxygen or sulfur, R is alkyl having 1 to 4carbon atoms and R is alkyl having 1 to 4 carbon atoms or alkoxy having1 to 4 carbons (2) water and (3) phosphoric acid.

2 Claims, No Drawings STABILIZED AQUEOUS SUSPENSION OF PHTHALIMIDOMETHYLMONO THIO-OR DITHIO- PHOSPHATES OR PHOSPHONATES This invention relatesto a stabilized aqueous suspen- 5 sion of certain phthalimidomethyl monothioor dithiophosphates or phosphonates with phosphoric acid.

The certain phthalimidomethyl mono thioor dithiophosphates orphosphonates are those having the structural formula where X is oxygenor sulfur, preferably sulfur; R is alkyl having 1 to 4 carbon atoms,preferably methyl and R is alkyl having 1 to 4 carbon atoms or alkoxyhaving 1 to 4 carbon atoms, preferably methoxy. These compounds areknown insecticides and evidenced by US. Pat. No. 2,767,194 and others.

These compounds are stable when formulated with organic solvents howeverthey decompose when formulated as aqueous suspensionsin hard water(water having a pH above 8.0). The exact method mechanism of thedecomposition is not fully understood; however, it is theorized thathydrolysis of the compounds occur when they are exposed to such water.

Generally the decomposition causes no serious limitations in the use ofthe compounds as insecticides. However, in applications where aqueoussuspensions of the compounds are stored for long periods of time,several weeks, deleterious decomposition of the compounds has beenobserved. An example of such applications would be dipping of cattle inlarge vats to control various insects and ticks. In such dippingoperations it is desirable to use or store the dip vats over longperiods of time such as several weeks or months.

Quite unexpectedly it has been found that phosphoric acid greatlyretards the rate of decomposition of the recited compounds when they areused in aqueous solutions or suspensions.

Although it is known in the art that aqueous solutions of the aboverecited compounds are rendered more resistent to hydrolysis by loweringthe pH of the solution, the unexpected and superior results obtainedfrom the use of phosphoric acid can not be explained.

The phosphoric acid can be added to the recited compounds either byusing phosphoric acid or by forming it in situ from such compounds assuper phosphate.

Even the smallest amount of phosphoric acid is useful. However, it ispreferred to utilize about 0.01 to 0.5 percent by weight of water, andmore preferably 0.01

to 0.05 percent by weight of water to stabilize the compounds for longstorage.

Stabilization is best achieved by uniformally dispersing the phosphoricacid throughout the solution or suspension of the recited compounds.

The stabilization of aqueous suspensions of the phthalimidomethyl monothioor dithiophosphates or phosphonates with phosphoric acid isillustrated in the following example.

EXAMPLE I The following formulation is used in a test to determine theeffectiveness of N-(mercaptomethyl)phthalirnide-S-(0,0-dimethylphosphorodithioate) againsthouse flies before and after treatment with phosphoric acid.

Parts by weight I. N-(mercaptomethyl)phthalimide-S-(0,0-dimethylphosphorodithioateJ 54.74 2. Kaolin clay 28.86 3. Sodiumalkyl naphthaline sulfonate 0.40 4. Sodium lignosulfonate 6.00 5.Hydrated silica 10.00

The above formulation is prepared in a 5 liter suspension at 0.05percent active ingredient. A reference vat is prepared and the pH isadjusted to 8.5 from 7.5 using 130 milliliters sodium hydroxide tosimulate hard water.

A second identical vat is prepared using 130 milliliters (0.1N)phosphoric acid.

Each vat was bioassayed at O, 4 hours, 1, 5 and 9 days, afterpreparation to determine any decomposition of the active ingredient. Theresults are recited in Table l.

7 TABLE 1 LD,,,, Values rig/25 H.F.*

Phosphoric Hard Water Time Acid Vat Vat 0 hours 1.8 2.3 4 hours 2.3 5.01 day 1.9 5 days 2.5 9 days 1.8

f Values of 2.0 to 2.5 are normal and acceptable insecticidal values forthe active ingredient of the formulation.

wherein X is oxygen or sulfur, R is alkyl having l to 4 carbon atoms andR is alkyl having 1 to 4 carbon atoms or alkoxy having 1 to 4 carbonatoms, water and The Composition of Claim 1 wherein X is Sulfur, Rphosphoric acid in an amount of 0.01 to 0.5 percent by is methyl and Ris methoxy.

weight of water. 5F

1. A STABLE INSECTICIAL COMPOSITION COMPRISING AN INSECTICIDALLYEFFECTIVE AMOUNT OF A COMPOUND OF THE FORMULA
 2. The composition ofclaim 1 wherein X is sulfur, R is methyl and R1 is methoxy.